Britain has offered its full backing for a renewed military offensive inside Pakistan, as UK ministers confirmed the country was now "part of a single campaign" alongside Afghanistan.

Defence secretary John Hutton said the UK supported targeting Pakistan-based Taliban and al-Qaida positions and urged Europe to begin offering assistance to eradicate insurgents in the tribal regions bordering Afghanistan.

Confirming that Britain was being drawn into a widening regional conflict, Hutton said the time had come to target Taliban and al-Qaida havens inside Pakistan. In his most explicit statement of intent against Afghanistan's troubled neighbour, Hutton said that the military objectives in the region must now have "an equal focus on both countries".

He added: "AQ [al-Qaida] is in retreat, scuttling across the border into Pakistan. Trying to buy time. Desperate to regroup. That is why there must be no let-up ... there can be no escape, no hiding place."

He indicated that Britain, which has deep historical ties with Pakistan and remains its largest trading partner in Europe, must play a principal role in supporting the American military effort in the region.

The defence secretary said: "In Europe, we can no longer offload the tough questions about how we deal effectively with AQ and the Taliban in Pakistan to the US.

"The political burden of dealing with the Pakistan side of the border must be shared. And there are many European countries with strong ties to Pakistan that can more effectively share that burden with America."

However, the US tactic of targeting senior al-Qaida figures using drones inside Pakistan has drawn international condemnation and undermined public support in Pakistan. The country's Foreign Ministry spokesman Abdul Basit warned recently that Islamabad regarded "drone attacks on our territory as a violation of Pakistan's sovereignty and definitely counter-productive".

An MoD spokesman said that Britain was ready to offer military, political and diplomatic support to a renewed offensive in Pakistan's tribal lands, but what precisely that entailed was dependent on the resources other Nato members were prepared to offer. However, the initial aim would be to support the Pakistani government, rather than place British forces on the ground inside the country.

US officials yesterday indicated that attacks along Pakistan's western frontier, apparently by unmanned CIA aircraft, would continue, amid speculation that coalition ground units may begin crossing into Pakistan's borderlands at some point. A Pentagon spokesman, lieutenant-colonel Mark Wright, told the Observer that the US had already offered to launch "joint-military operations" with Pakistan's Frontier Corps in the tribal areas.

The most recent evidence that Pakistan was becoming an increased focus of concern surfaced last week when Gordon Brown pinpointed al-Qaida in Pakistan as the greatest threat facing the UK in his national security strategy. Two thirds of terror plots uncovered by British intelligence agencies have a Pakistani connection.

Additional military resources are also likely to be deployed to the region once Britain withdraws its 4,000-strong force from Iraq this July, with moves to increase troop numbers in Afghanistan from 8,300 to potentially above 10,000 within a year.

The new-found focus on Pakistan will dominate Nato's 60th anniversary summit in Strasbourg this week, in which Britain and the US will attempt to drum up more support for the twin Afghanistan and Pakistan - AfPak - mission. President Obama has promised an extra 21,000 troops for Afghanistan on top of the 38,000 US troops already there. By contrast, Nato has sent 32,000, with Germany so far sending just 3,640, France 2,780 and Spain 780. These three countries will, say Nato sources, be under pressure to increase their contingent.

Defence officials in Whitehall are increasingly exasperated that, even as the conflict broadens, prominent Nato members are not pulling their weight. Hutton condemned "the massive leadership imbalance" between Europe and the US in Nato. He added: "It's an imbalance set to grow in the coming months as America commits vastly more resources of every kind to the mission in Afghanistan."